The survival and development of embryonic chick ciliary ganglion neurons are being examined in dissociated cell culture. Factors are being isolated and characterized that influence the development of cholinergic properties by the neurons. Cell culture conditions are also being sought that permit the normally cholinergic neurons to express novel differentiated properties characteristic of other neural crest derivatives such as the synthesis of catecholamines. Experiments are also being carried out on the specificity of synapse formation by ciliary ganglion neurons in cell culture. Studies with protein neurotoxins are being done to develop a specific ligand for studying regulation of the neuronal acetylcholine receptor and for studying the internalization of membrane components by neurons.